Museums have traditionally used timelines
as a means of creating narratives of historical, cultural, political, geographical
and social change. However, such timelines are only one aspect of a potential
infinity of semantic continua, and fail to exploit fully the possibilities
implicit in the objects that exemplify them. In this paper we describe the
'Gernsback Machine', a novel categorisation and navigation model based on
principles of facet analysis that enables descriptive metadata terms to be
located within a fully navigable universal facet tree. The navigation potential
of 'step, flip or zoom' inherent in the GM permits exploration through all
semantic continua, and, by allowing the users to follow their own particular
threads, enables complex narrative structures to be created. We describe how
the Gernsback Machine can be used to create a virtual museum space for new
or existing collections, using a series of recursively defined 'bento' containers
to define the museum content. We describe how our prototype illustrates the
potential of the GM in exploring different aspects of the time facet, in a
'museum of the history of possible futures and probable pasts'.

Introduction

History is the science and art of the
plausible construction of narratives out of such fragments as we have been
left by the havoc wrought by time. Museums have traditionally used devices
such as timelines to create these narratives. The simplest timeline may illustrate
only a single theme, with historical events or occasions mapped against a
chronology; more complex ones weave together parallel streams to produce a
rich network of explicative narration (e.g. Rock+Roll Hall of Fame Museum,
http://www.rockhall.com/; Metropolitan Museum
of Art Timeline of Art History, http://www.metmuseum.org/toah/splash.htm;
Natural History Museum's Dino Directory, http://flood.nhm.ac.uk/cgi-bin/dino/index.dsml).
The history of the human race may be represented through a superimposition
of the facts of fashions, reigns, civilisations, lives of famous people, culture,
and technology on a common linear axis, with parallel streams sometimes representing
these different threads of narrative for the same locale, and sometimes different
physical or geopolitical locations for the same time-display.

Underlying all timeline displays is a
set of presumptions that go overlooked and mainly unchallenged: these are
to do with the commensurability of events, the correspondence between narrative
structures, and the implicit assumption of the universal subjective temporal
standpoint which McTaggart (1908) called 'the unreality of time': the
'God's-eye-view' that permits such temporal arrays to be strung together like
beads on an abacus, each with its own measure but each in its role in the
greater system. Fraser (1975) draws on Uexkull (1934) to show that such constructs are necessary
subjective knowledge structures created by our sense of time, which belongs
in a noetic umwelt overlaying
the physical. Luce (1972) shows how our time-sense and hence our
co-ordination of time's passage are necessarily embodied, and how the very
selection of scale for time recording takes for granted much that must be
considered in presenting a succession of events tied to a series of circadian-based
sense impressions.

It is not that such systems are inaccurate
or inappropriate, but rather that their use implicitly entails continuously
ascending and descending a tree of interoperability to work (Figure 1). Any
use of a timeline will always involve this reinterpretive nature, and this
is especially significant whenever different term-sets (e.g. 1620s, 17th
century, Jacobean, Renaissance) are used to describe the same moment in time.

Figure 1. Tree showing organisation of time concepts.

Every comparison between a sociological
view of history (reign, lifespan, generation) and a chronological one
(century, decade, year) involves backtracking up this tree to the nearest
common point and down again to the desired scale. As we see from Figure 1,
the common ancestor for both sociological and chronological time is linear
time. However, to move from a moment expressed as linear time to the same
moment expressed as circadian time involves reference to the root node
of the temporal tree.

Consider an example: a late summer day
in England. We can determine the linear senses easily enough - sequential:
19:00/196/1911 CE; chronological: Saturday, 15 July 1911 AD; historico-political:
Eventide, St Swithin's Day, Coronation Year of King George V; sociological:
Edwardian/Georgian period - and we can move between them by common reference
to the parent node of linear time. Similarly, we can move to the circadian
sense (e.g. natural: early evening, midsummer; or sociologicallydetermined: stumps, Saturday's cricket match) by drawing on the explicit
alignment of the linear temporal with the circadian, an alignment inherent
in temporality.

We can appreciate this concept more clearly
if we make a small change to one of the received facts. If we change the historico-political
value, so that we are now in the coronation year of George VI, rather than
George V (but still Eventide on St Swithin's Day), then the only value that
changes for the sequential is the year (1937 CE); the day of year (196)
and time of day (19:00) will not alter. However, the social sense
of the moment has gone from the golden dawn of a new century to the darkness
of the Depression with the threat looming of a new European war. And the significance
for the circadian values is considerable: while on a mundane level
the day is now Thursday, and has all of the appropriate sociologically-determined
circadian associations (workday, not half day), on a more sophisticated level
it is unlikely to be an occasion for cricket, and much less likely to be a
celebratory occasion (being further away from the Coronation date, and in
a time of great austerity). On the other hand, the natural circadian
sense (early evening, midsummer) remains untouched, as indeed it should.

If on the other hand the coronation were
that of King George IV, while the change for the sequential would have
had been similar (i.e. a change in year only), for the other senses of time
the differences would be considerable. The sociological senseof
the moment would be placed in the turmoil of Georgian England, and while it
again happens to be a Thursday, it would be the Thursday four days before
the coronation, and the likelihood of celebration would have been high
(although the prospect of cricket negligible).

We can see from these examples that, by
having common ancestral terms, the inter-operation of the timescales can be
guaranteed, and this is the mechanism that validates the parallelism that
is involved in the multi-timeline display. As we shall discuss later, the
tree structure in Figure 1 has all invocations of the temporal that are required
in timeline displays, and any timeline display will always involve one or
more of these categories.

Another way of examining the timeline
is from the point of view of the signifiers marked along it: in other words,
from the perspective of the subject matter that applies at the particular
date. So our various interpretations of the point in time (19:00/196/1911
CE) become 'Sport, Edwardian, Cricket' or 'Harvesting, Early 20c, England'
or any other combinations. The delineation on the line now becomes one of
the interactions of several possible subjects of interest, and the secondary
(i.e. non-temporal) significances are a matter of the implicit subject
of display - to be in this timeline, it must have this feature.
The problem of timeline representation then becomes one of multiple subject
classification, one of which is always time.

The problem of classifying the temporal
in determining the subject matter of documents is of course a constant problem
for bibliography, and Ranganathan's (1959) distinction of a temporal 'facet' offers
an insight for our timeline study. Time is only one of several continuously
interacting facets of meaning operating in any high-level description of a
set of facts, and to give meaning to the description must interact with other
facets (space, matter, personality, etc) to give a clear understanding of
the subject at hand. And every point in a timeline that has a spatial or material
significance can also be represented as a point on a spatial or material continuum
(effectively a 'space-line' or a 'matter-line') where the point has a temporal
significance. We can then see that a timeline is a specific form of a generalised
facet continuum, and that all such continua will have a primary facet
which determines the nature of its contents, with secondary, tertiary, and
so on facets qualifying the meanings of the labels used.

We can see equivalent semantic organisational
hierarchies for facets other than time. The facet-tree in Figure 2 describes
extension in space, showing, for example, political features
(empires, nations, alliances in time) or ecological features (marshlands
and beaches in recent history indicating global warming).

Figure 2. Tree showing organisation of space concepts.

In a similar way, we can describe a matter
tree, for examining the instantiation of the agent and background for depicting
historical events (Figure 3).

Figure 3. Tree showing organisation of matter concepts.

Beyond the root nodes of these individual
facets there can be conceived a single facet tree which informs all these
continua. The richness and evocative power of this tree lies in the large
amount of symbolic content that can be placed within its framework. This is
why timelines per se are so popular and ubiquitous: they have great
psychological appeal, as if one had a glimpse into the engine of history,
and could see the effects of causality embedded in its fabric.

Let us now return to the idea of timeline
as narrative. When such timeline-based displays are conceived, their designers
are effectively creating a narrative to convey a sense of time's passing to
the intended audience. The events, occurrences or periods chosen for display
(and perhaps more significantly, the artefacts chosen to exemplify them) are
drawn from the designer's world-view, for all that they invoke the universal
objective that McTaggart criticized. And when we place a series of artefacts
in a line like beads on a wire, they are made into a pattern that conveys
an idea of temporality, but their essentially quantal nature might equally
well tell another story that fitted them.

This multiple interpretation is of serious
concern to the exhibition designer - the effect of revisionism on older exhibits
is to make them exposed to ridicule, for all that they had serious intention
in their design. A review of art histories by Elkins (2002) shows a dangerous reliance on the European
Leonardo to Picasso period, with a distorted view of the rest of human creativity.
When Gould analyses historical timelines (Gould, 1987), trees of life (Gould, 1989) and categorization of race (Gould, 1981) he shows how much the designer
serves as an unconscious interpreter for their audience.

Paradoxically, however, this polysemy
is also of great potential benefit to the designer of such exhibitions. Given
the multiplicity of potential interpretations for any point in the timeline,
and for any artefacts instantiating that point, the question becomes one not
of designing a timeline, but rather of selecting an interesting one from the
myriad narratives implicit in the artefacts themselves.

The act of collecting and preserving that
is the raison d'etre of museums cannot predict what will end up being important,
nor can it say with any surety what was once important. But when making an
exhibition, a pathway can always be drawn to connect and explain certain objects
within a hypothesised narrative structure. This applies not only to the curator,
but also to the museum visitors, who can select their own paths through an
exhibition from the many possible ones that may be of interest. And the power
of such narratives as educational and research tools is obvious: by creating
time- and space-lines to record the contents of a collection, the users can
create their own information matrix in that collection's holospace.

However, not all exhibitions will be coherent
merely from the happenstance of their conjunctive orthogonality - there must
be an intelligible rationale if the entire system is not to be become chaotic
or anarchic in its presentation. So the challenge for the designer of such
a museological information system is to try to restrict the potential to the
plausible and interesting, without imposing too fixed a view onto the process
of timeline creation. This leads to the establishment of a possible framework,
not only for classifying objects in a collection, and for displaying them
in timeline-based tours, but also for a systematic subject/facet-based interaction
between collections that are geographically distinct, either within a multi-homed
collection, or between different members of the museums community.

Bearman and Trant (2002) in a recent
critique of museum Web practices, observed that increased access to independent
sources of knowledge has not yet led to an emergent unified museum-based knowledge
resource, as the Web currently 'takes little advantage of the interrelationships
between and among disparately located museum objects'. They go on to state
that 'museums' collective knowledge can only be identified, navigated, explored
and integrated if its structure is explicitly declared (Bearman and Trant,
2002, 5).

In this paper we present a prototype for
a virtual on-line museum that permits visitor-constructed narratives for museum
exhibitions within a multifaceted, interrelated information space. The categorisation
and navigation model at the heart of this system - the Gernsback Machine -
permits novel types of exploration along all facets of meaning for any object
or grouping of objects, and the system itself can draw on both local and Internetworked
resources.

The Gernsback Machine

At the heart of the Gernsback Machine
is a set of facet categorisations that determine the applicability of values
to all of the objects within a collection. It is this commonly determined
yet distinct categorisation system that enables the Gernsback Machine to perform
its twin roles of cataloguing and navigation. The selection of different faceted
termsets is an integral part of the process of accession and curation, and
of the virtual museum's tour experience.

Our framework draws on Ranganathan's facets,
but recognises the need for rich cultural (and more significantly non-book)
materials to be represented in the multiple dimensioned trees that we have
already described above. Each facet has a matching branch of a single unified
facet tree, and the four levels of the branch give an invariant framework
for scaling the appropriate continua and enable the collection objects to
be located and navigated.

The Facet Tree

Despite a preponderance of metadata schemes
and schemas for organizing metadata and encouraging metadata interchange,
there remains (Doerr, Hunter, & Lagoze, 2003) a cultural
relation aspect to most metadata use. When use has been made of traditional
library science organizing principles such as Dewey (OCLC, 2004) and LCSH (Library of Congress, 2004), the tendency has
often been to map the most likely occurrence of an artefact (i.e. to facilitate
retrieval), rather than use them to indicate the semantic richness of an artefact.

Rather than take this approach, we have
drawn on the Facet Analysis system's ability to represent the knowledge embodied
in objects with the maximum amount of polysemy, and so make the consultation
process much more informative. By maximising the points of access into a system,
we maximise the likelihood of an inquiry being successful, not the
case with single mode classification systems.

Facet analysis can be seen as an attempt
to get a unified location of 'slot/descriptor' pairs within an intellectual
universe of discourse. In this it presages the frame model of knowledge representation
(e.g. Minsky, 1981), and it can be used to inform
a frame-based media/collection description system. In drawing on the facets
to organise our metadata-rich media artefacts and the objects for which they
are proxy, we are proposing a new organising principle based on the facet
classification system and applicable not only to existing metadata
stores, but also to existing metadata schemas.

(It is important to note that in some
knowledge management and information retrieval literature we find a different
use of the term 'facet', to describe a common system of headings for metadata,
and to group lists of descriptors under those headings: in contrast to our
usage, they present a faceted information space as one partaking of the grouped
slot/term pairs, rather than the systematic that informs them.)

We have already introduced three of the facet trees in the
Introduction: those for time, space and matter. There
are corresponding trees for the remaining Ranganathan concepts (personality
and energy), and to these we also add one for ontology and one
for causality. These two additional facets are necessary because of
the nature of the museum exhibitions that are to be supported: ontology
because we are drawing comparisons between objects and sets of objects,
and need to show how they fit together in relation to each other and the world,
and causality because part of what we are trying to establish is a
way of depicting the relations between the objects, especially when trying
to illustrate complex object relationships in an historical setting.

We describe the facet trees in general
terms here, and defer a complete discussion of their structures to another
paper. Each facet tree has four levels - facet, domain, quality and
measure - with each level considered a dimension of the termset that
is used to determine the value of the object (Figure 4). These four levels
are the minimum to get a necessary and sufficient set of terms to clearly
define a termset. The application of a term to an object results in a value:
to reconstruct that value, the full termset must be recreated as an enfolding
context. Each path down a facet tree from node to measure represents distinct
categorisations of values that cannot be mixed or translated without losing
information or (worse) committing category errors. This is a significant point,
as it is the manner in which we can underwrite the intelligibility of the
classification practices involved from facet to value.

Figure 4. Part of the facet tree for Time showing (from
top) dimensions of domain, quality and measure.

At the top of the facet tree is the root
node, which corresponds to the facet itself. Below the root node is a dimension
that represents the universe of discourse or domain within which the
term operates. Although domains partake of the same facet, generally they
are incompatible with each other - they are describing different experiences
of the same facet. In the example of the time facet, the three domains (linear,
circadian, and cyclical) are actually incommensurate - there are no one-for-one
equivalences possible between them. Of course, some values (such as linear
chronological values) will have components that may be translatable by reference
to an absolute table of correspondence, but generally to consider one domain's
value from the perspective of another is to commit a category error.

The dimension below the domain, quality,
does however permit inter-translation. Here the ways in which the value can
be applied to the object are regularised. The qualities within a domain are
compatible with one another, but operate within different terms of reference.
In our example in the introduction, we showed the different ways in which
a point of time could take linear values.

Below the quality dimension is measure.
This is the level at which the mechanism for description for the subject is
determined: it can be selection of a units system, it can indicate a preference
for vocabulary or customary use, or it can be indexical to an external authority
that will act as a source for terms. In Figure 4 some of the measures for
linear and circadian time are indicated. Here the examples elaborated in the
introduction can be mapped out, and the correspondences clearly seen.

Thus, when we have the four reference
points of facet, domain, quality and measure set,
then the domain of application of the termset is established. The termset
determines a value for the object, and that value is uniquely defined by that
termset.

Navigation

The facet tree is used to retrieve objects within a collection
by choosing a termset from the facet tree, and selecting values within that
termset to use as search terms for the objects. Each selection of termset
+values makes a constraint set (or heuristic), and application of an
heuristic results in a set of objects that satisfy its being returned (the
ambit of the heuristic). Repeated application of heuristics and movement
within an ambit are what enables navigation through the museum space. Several
constraints may be applied concurrently, permitting complex heuristics to
be developed.

There are three types of operation possible within the
collection space. We can move from one object to another either within or
between ambits; we can change the heuristic so that it includes more or fewer
objects in its ambit; or we can shift the focus of the system to another ambit
entirely. It is these three core operations that determine our systems navigation:
stepping between objects, zooming the heuristic (increasing
range or increasing detail) and flipping the view (shifting the path)
between ambits.

Stepping is the main navigation mode in the Gernsback
Machine. It is how we proceed from one object (or composite object) to another.
With step, we move in a direction from one object to the next in the currently
selected continuum. Alternatively, movement can be in graded measures along
a continuum (when there do not have to be objects present for those gradations),
e.g. moving along a timeline one decade at a time, or synchronizing several
sparsely populated timelines.

Zooming involves either changing the measure at
which the ambit is viewed (e.g. from century to decade), or else changing
the range of the heuristic to take in more or fewer features on the same measure
(e.g. viewing one, three or five centuries on the displayed continuum). Generally,
increasing the range of ambit increases the overview of the continuum, while
increasing the measure increases the resolution (the detail visible). The
zoom feature is also useful for orienting the Gernsback Machine when there
are no objects visible. Zooming out to maximum range enables the entire collection
space to be seen as a whole, and the user can then home in on the regions
that are populated. Zooming in on the areas that are densely populated can
enable the user to see the object disposition in finer detail.

Flipping is the least familiar of the GM navigation
modes. It serves to re-ordinate the ambit through the use of shared metadata
that is not related to the current heuristic. To understand this, it is necessary
to remember that the metadata which is not responsible for placing
the object being viewed within the current ambit will share potential heuristics
with other objects that are also not in that ambit. In flipping, any given
term from an object's metadata set can serve as a query-by-example navigation
system to show other potential heuristics the object may exemplify, and those
other objects which either share common or adjoining values with the current
object in alternate continua. The user can then flip from the current continuum
to one of the alternate continua, with the current object still the centre
of focus.

As an example of flipping in action, consider a meeting
of several captains of the fleet in the wardroom of a galleon in 1625. If
it were a meeting of different nationalities, then the heuristic that the
meeting exemplified (say of chronological time and nominal space) could serve
as the pivot to enable the user to flip around to the maritime activities
of any one of the nations (but only one of them) present. However, the situation
could also pivot on the designer of the wardroom, or the writer of the report
being read, or any other such metadata.

The significance of this feature is that it is a navigation
by network - by the very interconnectedness of the elements of data -
and this is the type of connection in an information space that is the most
difficult to explore (it is incredibly costly in processor resources) yet
the most intuitive to experience. What is more, a navigable graph is the only
form of pathing through an information space that is guaranteed to cover every
object.

After each navigation operation, the new continuum is itself
the subject of stepping, zooming and yet more flipping.

A session with our hypothetical maritime museum would include
all these navigation modes seamlessly. The user would search for a value ('La
Perouse in Sydney Harbour'), find adjoining information by stepping (the First
Fleet) and then see where one of the First Fleet ships went next (flip). From
that ship's next flotilla engagement (step) we could zoom out to the entire
fleet, then flip to the Admiral in charge. Following a letter home from the
Admiral (flip) might lead to a discovery of 17th Century child
illness (flip), thence to 17th Century medicine (flip), and so
on.

Building A Gernsback Machine Virtual Museum

In this section we describe the architecture
required for our museum, and how we have implemented the prototype. We then
describe the process of constructing a virtual museum based on this architecture.

Architecture

The virtual museum space is a digital
domain that represents the collections within a museum or group of museums,
but which is separate from it. In essence it provides on request annotated
displays of media artefacts that represent either the objects in the collections
or associated material. In the context of exhibitions the museum will also
include reference material and navigational aids (maps, lists etc) so that
within the museum space there is a universe of information that is complete
in itself.

Practically, the museum is a combination
of a database, a metadata system and a media-server, working through an application
facilitated by a Web-server.

The base level unit in the museum space
is a containerised media resource with a metadata halo, which we term the
'bento'. (A bento is a Japanese tray or compartmented lunch box, designed
to hold different items of food. Apple used the term to define their 'Bento
Specification' in 1993 for a platform- and content- neutral data wrapper.
However we use the term here in its more general descriptive sense and do
not make use of the Apple specification, or any other implementation, in our
project.)

The bento has three characteristics that
are important for the GM: it contains standard 'media slots' that can be filled
with simple or complex media artefacts; it is completely self-descriptive
with metadata (subject, technical, structural and administrative); and, importantly,
each bento is potentially linkable with any other, constrained only in a semantic,
not a technical, sense.

Formally the bento is a frame:
it contains data to describe itself, contains a dictionary of values, and
maintains details of links with other bentos. The frame is a standard knowledge
modelling format which has had great success in knowledge management, and
the bento, by maintaining both the media artefacts and the pertinent metadata,
serves doubly as cataloguing and navigating instrument. Since the bento can
store media artefacts and access their metadata transparently, it follows
that it can contain other bentos as well, and this mechanism can be as recursive
as is necessary.

In Figure 5(A), the bento is laid out
like the components of the lunchbox. As it is a frame, it has its own identifying
metadata (including ownership, copyright, purpose, accession or creation details),
references to related bentos (as a means of organising the bentos in sequences
and modules) and can also identify media artefacts for which it is the parent.
The AVI component in (A) is in fact itself a bento, and the blow-up in part
(B) of the same diagram shows how it internally has its own metadata component.

Figure 5 - Bento architecture

This structure makes the bento the ideal
vehicle for recording the sequences of media artefacts necessary to instantiate
a virtual tour of the museum, and by an ordered mechanism for creation and
display, a single bento becomes all that is necessary to contain the entirety
of the tour and its accompanying metadata. The lower order bentos in the hierarchy
will then be self-organising, and an instruction to the top level tour bento
to display next component, previous component, restart, time left in tour
or even print/export will be dealt with at the top level.

Such a tour will consist of two types
of bentos: those that contain artefact bentos with rich descriptions, and
those that act as segues, standing in between other bentos and providing any
necessary semantic buffering. The annotated bentos could then serve as building
blocks to many other tours as well as the tour in which they are being included.

Since the bento provides both the content
for the museum and its navigation potential, it is designed to enable the
objects' information also to be retrieved from the system for the purpose
of aligning the object with the continua, as part of a visitor's querying
the GM. This means it can not only display the media artefacts as they occur
within a tour or query result set, but each one can also display potentiality
for further digressive navigation options, in the explorative manner outlined
above.

In terms of guarding intellectual capital,
bentos can also ensure that no object or representative artefact is ever displayed
without the context of copyright, watermarking and precedent details, and
can mediate these when the exhibition is derived from many different real-world
institutions.

Figure
6 shows the recursive nature of the bento, and defines some terms that we
shall use later in describing our museum space.

Figure 6 Recursive bentos forming museum structures.

Implementation

The prototype museum database is a hybrid structure of
authority tables, hierarchical metadata sets and standard data records. The
challenge was to develop a design for a bento structure that permitted the
maximum freedom for the content developers, while permitting the full potential
of the GM navigation structure to be available, and to provide as seamless
a way of cataloguing as possible to provide the full metadata description.

It was decided to make the GM's own native data format
XML, and although the actual XML data is stored in a relational database,
it is viewed and edited in XML form. There are two main XML trees involved
in its implementation. Primarily there is the bento-space for recording the
details of the bento material. This is done in our own XML dialect, as a KRL
(frames are usually recorded with a KRL). The namespace is established with
reference to knowledge management and expert system current practices, to
ensure adaptability.

The secondary XML tree is the facet tree, which is made
from the original Ranganathan set, with our own isolates extended via the
three lower dimensions. The facet tree is based on general principles of faceted
classification systems and the various compound classification systems and
metadata ordering systems currently in use in the museums and library communities,
such as AAT, ULAN, and TGN (Getty Vocabulary Program, 2004). This tree serves
as the basis for the interoperability between the user and the museum - informing
the dialogs and organising the material. Extensive term lists are not included
in the tree, as (apart from reasons of efficiency) the actual values are either
resident in other systems or are derived from the bento-space. The entire
tree (about 300 termsets) plus candidate values (from the trial set and the
external lists - about 4,000 terms) are extracted from the system in various
XML metadata standards such as XFML (XFML, 2004), Topic maps (ISO/IEC, 2002)
etc, and analysed for full coverage of the facets and their domains.

The result sets are created by an X-PATH match between
the two XML systems, and the results displayed using an XSLT transform. This
was done to make the solution as universally acceptable as possible.

An initial bento dataset (about 50 items) was populated
by hand, with a view to seeing the architecture populated as soon as possible
to test the interactive aspect of the GM. Media artefacts were created, together
with appropriate metadata, and these were used to build up tours and exhibits.
Although minimal curation was done, sufficient words were entered for the
segue bentos to build up appropriate bento tour sets.

The bentos themselves were drawn from several different
sources, and identified primarily by the space and time facet metadata. Multiple
continua for time and place were established and explored.

Process

The museum when operating works by presenting
a common interface to acccessioner, curator and visitor: they are all effectively
different levels of user. This is necessary because when the Gernsback Machine
is being used, the various controls that establish the presence of termsets
represent the context for the value being applied. Therefore a matching dataset
must be in place when retrieving it.

The initial contact between the museum
and an object intended for the collection is at the stage of accession when
a user describes the object, and creates artefacts to represent it, by use
of the context-representation mechanism of the GM. This consists of selecting
a termset via the facet tree, and then (depending on whether the termset wants
a descriptor, a term picked from a restricted list, a referent to an external
table, a date, or a numeric value) entering a matching term.

Cataloguing an item for inclusion in the
virtual museum involves selecting an optimum number of terms to serve as retrieval
keys. This would be in conformity to pre-existing practice in the parent institution,
or if the virtual museum is a stand-alone concern, in conformance with the
best-practice museum cataloguing standards. These terms are linked back to
the termset when accessioned (i.e. the termset + value is stored as a key
in the bento).

This is where the GM comes into its own:
to perform such a task comprehensively is normally beyond the capabilities
of the museum staff (in terms of time and resources), but the metadata components
can be easily engaged either singly or as sets of metadata, while the action
of placing an object within a continuum can present a set of suitable values
to the user.

When curating an exhibition or tour, the
same process repeats itself - the material can be gathered by a faceted search,
and the items retrieved, and then the objects are lodged within the tour,
with a new metadata set pertaining to their proposed new role in the tour.
This process can reveal even more material as the collection grows in size,
and fully documented and annotated bentos become available for inclusion.

This is the same for all levels of the
exhibition - each time the same process of selection enables the curator to
draw on more and more semantically rich material, all of which is deemed to
fit the same faceted semantic halo (Figure 7). At each point in the selection
process, the material from the level of complexity below is retrieved by the
search, and that is the raw material for yet another bento layer.

Figure
7 Accession and curation process forming composite structures

In retrieving material from the museum, and therefore indirectly
finding potential tours of interest, the visitor to the museum repeats this
process. The difference between the visitor's displays and those to which
the staff have access is that the searches the visitor conducts are to an
extent managed. Not all material will be visible, and not all metadata will
be available for searching.

The collection is of course firmly grounded in the museo-informatic
community of practice, and so it is not only appropriate, but also necessary
to enable the virtual museum to partake in the common metadata initiatives
that are being developed at the moment. Because the facet tree is an organising
rather than an enumerating system, it is possible for the administrator to
make the system fully co-operative with on-line open systems initiatives like
the OAI (Open Archives Initiative, 2004). By having a hermeneutic layer built
into the system as a dictionary, either all or part of the OAI interface can
be implemented.

The public/private distinction that enables differentiation
between the scholar's access to a collection and that of the ordinary visitor,
or between the private access afforded an owner or curator and the public
generic interface, serves to make a distinction also between the local and
remote forms of the collection material. In the prototype, there is an ability
to have a 'second shot' approach at finding material - the user can request
that the search include remote material in addition to the local resources.
This approach has already been trialed successfully with the NCSTRL (Networked
Computer Science Technical Reference Library, 2004) repositories, and in the
end it is more a question of reliability and certainty in making the mappings
than a question of technological limitations. And from this point it is a
small step - albeit one requiring a fair degree of co-ordination - to Bearman
and Trant's (2002) metadata-controlled collection interoperability. The use
of a public/private metadata distinction permits the GM interface to pick
up on a distributed and decentralised set of objects displayed upon a series
of continua.

Design issues

The problems of disappointment and letdown from a visit
to a virtual, rather than an actual, museum are well known. The haptic and
kinetic experiences of realia are part and parcel of the curator's art, and
the design for the computer experience is a greater challenge than the recreation
of the experience of cinema for television. Over and above this problem is
the challenge of designing the system for the principle of least surprise,
of not stopping a visitor to the virtual museum because of an unfamiliar interface.

The challenge for the user interface design is to ensure
that the visitor's three fundamental concerns of Where am I?What's
here? and Where can I go? (Veen, 2001) are addressed; while making
available (but not overwhelming) the unusual navigation potential of the Gernsback
Machine, based as it is on an unimaginably large information space that has
no physical analog, and possessing a navigation operation (flip) that is unlike
anything normally encountered.

It is well know that since users are only ever presented
with a single screen, there is no inherent sense of the larger structure that
sits behind that single page. Therefore, enough information needs to be conveyed
within the page to invite further interaction. However, if this involves a
high degree of computer literacy, or following detailed instructions, then
a user without a compelling reason for exploring
the site is unlikely to persist with the interaction.

A particular challenge is how to represent the potential
of the 'step, flip, zoom' navigation in an intuitive manner. The default set
of interface controls that we have developed are similar to the slider controls
on a graphic equalizer, but they each have an informatic property to match
a dimension of the GM. The four sliders correspond (left-to-right) to Facet,
Domain, Quality and Measure, and the option to select a value from a pick
list, enter a number, or retrieve a match is given to the user.

As the constraints are cumulative and additive, it follows
that there can be a potentially infinite number of such slider sets combined
to make for quite detailed searches. The interface enables these cumulative
queries to be created, and the individual constraints removed one at a time
from a running list of elements. If the display sliders are altered, then
the labels on the 2nd, 3rd, and 4th are reset
to blank, until a movement at a higher level re-enables them.

Of course, the slider sets that we have used here are only
some of many possibilities, including virtual reality interfaces, that would be
possible. Part of the designer's challenge is to create different consoles
to match different purposes.

Another challenge for the designer is to create exhibitions
out of the simple but raw outputs of the GM in making bento sets, which as
we have noted form the basis for the museum exhibition. By default they produce
an unsophisticated narrative told in terms of artefacts alone, with simple
labels derived from the metadata. Before the exhibition is ready for the visitor,
some additional design work will normally be necessary to ensure the exhibition
is coherent and attractive. Here the GM and the virtual museum can help the
curator and designer prepare a series of displays for an exhibition.

Examples

16th Century Ships

Our first example demonstrates the use
of the Gernsback Machine within a relatively conventional subject setting.
This hypothetical on-line museum provides a variety of virtual exhibitions,
which include both guided tours and free exploration. The museum home page
is shown in Figure 8, with three exhibitions, Ancient Eastern Dances,
16th Century Ships and Korean Dynasties.

Figure 8. Home page for on-line museum,
showing three available exhibitions

Guided tours

The visitor selects a desired exhibition
and enters its start page (Figure 9). This page shows the narrative structure
of the 16th Century Ships tour, set out as thumbnails along
a narrative line. The visitor may begin at any point within the tour. In Figure
9, the main narrative consists of the exhibits Navigation and Maps,
Trade Routes, Life on Board and Ship Building. Trade
Routes also branches to other related exhibits, Shipwrecks and
Re-enactments of Voyages.

The visitor clicks the 'Life on Board'
thumbnail and is taken to the Life on Board exhibit (Figure 10). The position
of the Life on Board exhibit within the main narrative of the tour is indicated
at the top of the page, and the alternative narrative pathways on the left.
The topics that make up the exhibit are shown as a navigable list at the top
of the page.

Figure 10. The Life On Board exhibit page,
showing the visitor's current location within tour (top and left), and topic
panels within exhibit (centre).

The visitor now has the options of exploring
the topics within Life on Board, or continuing to the next exhibit in the
16th Century Ships tour by using the top menu, or calling
up more detail on any of the individual objects in the exhibit. To view more
details about a particular museum object, the visitor clicks on the object
(e.g. Cutlery) and is taken to the object page (Figure 11).

The object page is the simplest level
available to the visitor, and consists of a description and media artefacts
(e.g. images, video) about the museum object, here a set of 16th
Century cutlery. From here the visitor may view other object pages within
Eating Utensils (Goblet, Bowl) or may return to the Eating Utensils panel
in the Life On Board exhibit.

Another option available to the visitor at this point is
to leave the guided tour, and embark on a free-form exploration of the exhibition
space. This possibility is indicated by a Go Exploring button and is
described next.

Exploration

To leave the tour, the visitor clicks on the Go Exploring
button on the object page. The page changes to exploration mode (Figure 12),
and the slider sets that permit the facet navigation about the selected object
appear. (Note that three slider sets are shown here, but, as discussed earlier,
the number is potentially infinite - in practice, the number of sets available
depends on the judgment of the designer and the limitations of screen real
estate.) The surrounding narrative structure disappears, as it is no
longer applicable in the free exploration (although a return to tour
icon enables the visitor to leave the exploration at any point and return
to their last place in the guided tour).

Figure 12. Object page in exploration mode,
showing facet sliders

Exploration begins when the visitor selects
a facet for exploration. It is important to remember that when considering
the object outside the context of the original tour narrative, there is no
single 'true' location of the object, and it is therefore up to the visitors
to choose what facet(s) they are interested in seeing the object located in,
and to continue navigating from that point.

For example, to see where the object was
located in time, visitors would select the Time facet on one of the slider
sets. They could then select to view where they were in Linear (rather than
Circadian or Cyclical) time, and within Linear, Chronological. Within Chronological
they might choose to view at a measure of Century, and the final value for
the object, 16th Century, would be displayed (Figure 12). The visitor
now knows that in terms of linear, chronological time, the object is located
in the 16th Century on a measurement scale of centuries. Equally, they could have chosen to view the object in
terms of Linear, Social time and found that the object was located in, say,
the age of colonial expansion.

Leaving any of the parameters in a slider
set unselected results in either arbitrary or default values being shown.
For example, a designer might choose to set defaults for domain and quality
to Linear and Chronological respectively, so that if only the Time facet was
set by the visitor, the most common concept of time, that of chronology, would
be displayed for the object.

The visitor may also set any of the other
facets to constrain further the description of the museum object. Other values
are not shown in Figure 12; however, possible values for Matter and Space
could result in the Cutlery object being described by 'cutlery, Dutch merchant
ships, 16th Century'.

Although the visitors have now constrained
the description of the original object within the parameters they are interested
in, other objects within the collection will also fulfil this heuristic. Clicking
a 'Show All' button at this point changes the display view to thumbnail,
and the original object is shown along with others that are located in the
same facet space.

The three types of navigation - step,
flip and zoom - that characterize the Gernsback Machine are now available
to the visitor.

Zoom navigation
occurs by altering the Measure slider, for example from Century to Decade.
Again, a different object set (but one that contains the original object)
is displayed: e.g. 'cutlery, Dutch merchant ships, 1580s'. Alternatively,
changing the measure of ship type could expand the view to 'all types of Dutch
ships in the 16th Century'.

Step navigation
occurs by stepping to the next century on the timeline, to see what other
objects are displayed, for say the 17th or 15th century.
A new set of objects is displayed. Stepping to a different value on the Time/Linear/Sociological
view of the timeline would permit a comparison with (e.g.) 'Post-Colonial',
while concentrating on the Space/Functional/Political would permit different
a narrative of comparison of nationality to be followed, and would retrieve
'cutlery, French merchant ships, 16th Century'.

Flip navigation
occurs by altering the quality or domain sliders. For example, to flip from
chronological to social time would return anything relevant from the social
age ('age of colonial expansion' or 'age of exploration') that the object
being viewed exemplified. Another flip (say on space to 'Functional/Political/Nationality')
would move to French or English maritime cutlery, and from there perhaps to
medical implements from the age, or to food preparation. The power of the
flipping mechanism is by its nature the most powerful for exploration.

The same principles of exploration apply
to the self-guided exploration of the visitor as to the curator who constructs
the guided tours: semantic coherence is best achieved by making only small
changes from set to set, rather than altering several facets at the same time.
Another factor that ensures the visitors are not overwhelmed by the vast number
of navigation possibilities is that they are constrained to navigate within
an exhibition, rather than the entire collection space of the museum. The
options available to them (on the slider sets) will therefore be constrained
accordingly (in our example, the visitors would still be exploring within
16th Century Ships- space, not within the Korean Dynasties or Ancient
Eastern Dances exhibitions).

As the exploration progresses, other tours in which the viewed object (or
set of objects) is used are dynamically displayed, and visitors can then choose
to jump to one of the tours and continue in a pre-written narrative again.
A trail showing their exploration path is also generated (blank in Figure
12), with the option to save for returning to later.

Extending The Timeline: A Museum Of The History Of Possible
Futures And Probable Pasts

Our second example illustrates the potential
of the Gernsback Machine navigation by concentrating on manipulating aspects
of a single facet, that of time. Our hypothetical virtual museum this time
is a museum of 'the history of possible futures and probable pasts'. This
museum draws on predictions of the future made at various times, both in the
past and in the present, from different sources (such as science, science
fiction, sociology), to create a media rich, interactive virtual space.

As we saw in the Introduction, a timeline
as commonly seen often uses the same continuum to express many different aspects
of facet-relative detail. However, a facet-line can convey token-reflexive
information as well - for instance with time, by showing a date, and then
pointing to the next day, the following year and so forth. Thus the next monarch
of the United Kingdom can be placed on a timeline after Elizabeth II, even
though the details are surmised (probably Charles III, but possibly William
V).

An interesting notion arises here: of expressing the multiple possibilities
of prediction (or with regard to the distant past, analysis) for the same
point of time. Our current present is, as the saying goes, 'yesterday's tomorrow
and tomorrow's yesterday'. We can see that there is an infinitude of token-reflexive
expressions for any point in time with reference to any other point in time.
It becomes a matter of selecting the interesting narratives from the many
possible ones and comparing them. So, we can compare the futures of Swift,
Bergerac, Verne, le Queux, Wells, Huxley, Orwell, Bradbury and so forth: it
makes sense to speak of a series of denoted presents for these authors 2004
[Swift], 2004 [de Bergerac], 2004 [Verne], 2004 [Le Queux], 2004 [Wells]
, 2004 [Orwell], 2004 [Huxley], 2004 [Bradbury]. We can envisage plotting
these futures on axes leading from their time of writing to the present with
a varying degree of detail. Within this context, it would be a simple matter
to cross-reference these dates with other faceted axes, as shown in Table
1.

Domestic transport

Communications

Entertainment

Society

Swift –
Lunatic republic

Servants

By dispatch

The same

The same

de Bergerac –
Voyage to the planets

Metallic horses

Mechanical

The same

The same

Verne –
Earth to the moon

Aerial ships

Telegraph

The same

The same

Le Queux –
The coming war in the air

Mini-dirigibles

Telegraph

The same

The same

Wells –
The shape of things to come

Flying cars

Radio

Programmed radio

Repressive technocracy

Orwell –
1984

Walking/ bus

Pneumatic tubes

Programmed TV

Brutal socialist regime

Bradbury –
Pedestrian/ F451

No pedestrians!

Telepathy

No books!/ Mindless soap opera

Repressive technocracy

Huxley –
Brave new world

Aerial moving footpaths

Videophone

Contraception and its consequences

Subtly pervasive technocracy

Table 1. The future as imagined by various
authors

Table 1 shows interesting contrasts in
sharp relief — how the future was a means of satire, of lampooning the present
for early writers, but a dystopian view, a means
of warning for later ones; and how the means of expression of the futures
reflected the technology of the time. The model can be extended further —
it is possible to see how (say) Huxley versus Orwell saw the poor in the future
(invisible vs. ubiquitous), or how foreign countries
were seen, or how change was expected.

A prototype version
of the museum has been implemented, and filled with some of the futurological
and science fiction of England and France from the 19th and 20th
Centuries. Using the Gernsback Machine, it
is possible to present concurrently on a single display the relevant details
and associated media artefacts of exactly such hypothetical futures as are
discussed in Table 1. Such analyses permit comparisons of same time/place
with different social strata for different authors, for instance comparing
Orwell's Proles with the leisure class of Huxley.

In a fully-populated museum, we could
also look at the 'pasts that never happened' - the 1965s of Orwell, Wells,
Le Queux and Verne, say, and see if it would be possible to get
to where we are now from there. We might also compare them with the 'pasts'
that are the staple of social advocates (both optimistic and pessimistic)
to see if they are any more plausible. At each stage of comparison the detail
can be fleshed out with comparative illustrations from book and film - a sense
of the continuous lives led by the different characters makes for a play of
Pirandellan synchronicity unfolding before the visitor to
the exhibitions.

In an interactive mode, the user could
examine the different continua for reasonable hypotheses: given what we know
about AIDS and global warming. How does that colour Huxley's gentle promiscuity,
or Verne's coal-power technocracy? As the timelines diverge between predicted
futures and our own past, comparisons can be made between the objects that
the writers chose to symbolise their imagined futures, and those that were
present in our past. We can imagine these metonymic tokens arrayed in their
own continua, yet compared along axes of attitude and intention.

This all makes for a fascinating tool
for research, enabling new methods, including statistical analysis of gaps
in the literature, with targeted sites for further research, and identifying
concentrations of influence between hitherto unrelated items. Enriched by
the superabundance of illustrative media artefacts in sound, picture and moving
image, it also draws one to think of Hesse's Glasperlenspiel
(Hesse, 1943) and of the intellectual game of infinite comparison of the arts and
sciences of the past and future.

Conclusion

The Gernsback Machine offers a new approach to the construction
and exploration of virtual museums. By recognising that time is only one of
several continuously interacting facets of meaning for any set of facts or
objects, the conventional museum timeline is itself seen to be only one representation
of a number of possible semantic continua that may be drawn through a collection.
The GM is a categorisation framework based on a facet tree that provides both
the definitions of the termsets used to describe objects, and the navigation
potential through the collection space, enabling exploration of these alternate
semantic continua in a way that opens up possibilities for new types of narrative
structures.

The facet tree that provides the twin functions of cataloguing
and navigating is indexical and integrates with existing metadata schemes
and metadata sets, providing the potential for metadata-controlled interoperability
of museum collections. The containerising and recursive nature of the bento,
the base level unit of the GM museum space, enables existing digital collections
and their metadata to be incorporated into new virtual exhibitions constructed
from logically-defined sources.

The GM provides a powerful tool for museum curators and
exhibition designers, and permits new visitor-constructed narratives of the
museum space. It also has great potential as a research tool, and has been
successfully applied in this manner in a separate project on the history of
programming languages (D. Pigott, unpublished).

Our back end prototype has demonstrated the proof of concept
of the cataloguing and navigation engine of the Gernsback Machine. Much exciting
work remains to be done to develop interfaces to support the curatorial process
and to explore appropriate metaphors and innovative interfaces for the visitor.

Note

We named our cataloguing and navigation model the Gernsback
Machine after Gibson's short story, 'The Gernsback Continuum' (Gibson, 1981), in which a man who leaves the
current space-time continuum after an extended period of photographing and
analysing futuristic art-deco buildings finds himself to have slipped sideway
through time into the Gernsback continuum. This is an alternate time continuum
to our own, wherein the future envisaged by the science fiction illustrator
Leo Gernsback has come to pass. The artefacts that are out of place and unimportant
in our continuum have become the most significant, while the buildings of
Louis Sullivan and Frank Lloyd Wright are marginalised. A subtext of the story
is the notion that there may be an infinity of such continua, one step away:
the essence of our Gernsback Machine.